Short Heath: Petrol in a Diesel Car? How Worried to Be
Far less than you likely are, provided it hasn't been started. Petrol sitting in a diesel tank does nothing to your engine till something draws it through the system — your ignition priming the pump, the starter, or the drive itself. So the fair answer to the first query anyone in Short Heath asks, "have I wrecked it?", is usually no. Petrol in Diesel is who to phone, with the engine left off, so it stays that way. What petrol actually does to a diesel, how to gauge how far it's travelled, and how to keep it from happening again: that's the rest of this page.
Inside the motor: what petrol in a diesel does
Diesel does two jobs on its way through a motor. It ignites, and before it burns it lubricates. Designed to very fine clearances, the injectors and the pump rely on the diesel moving through them to stop their surfaces wearing against one another.
The second job petrol does not do at all, and the first it does poorly. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump running on the blend to wear itself. It's equally made to resist igniting under compression — the opposite of what a diesel needs — which is where you get the rattling.
Put those together and the shape of the problem is clear. Not contact but circulation is what causes the damage. Where that petrol is only in your tank, it is a fault of fuel, nothing more. Whatever a worn pump sheds travels on, carried by your fuel, into the injectors downstream, which is why a pump that has worked on the petrol is where a mechanical fault starts.
Four scenarios our technicians see around Short Heath: how serious is petrol in a diesel?
Filled but not once started — as good as it gets. That petrol is in your tank and just that tank, and the task is a drain and a flush where your car stands. This is the one scenario that can only really happen at a forecourt, since anywhere else the car has been driven to get there.
Started for a second, or just your ignition on. The system has been bled, so petrol has left that tank and reached the fuel filter and your lines. That is usually still a straightforward job — a drain, a flush, and the fuel filter dealt with.
Your pump now worked a couple of miles on diluted fuel — that's what driving the car meant. How hard the vehicle was driven matters as much as how far, and the work takes in the tank, your lines, your filter and clean fuel through the whole circuit. Short trips, such as the school run to Oasis Academy Short Heath, are one matter. A run as far as Birmingham, under 5 miles away, is a very different task. So is any miles on the M6, under 3 miles from Short Heath, where your engine has been running hard throughout.
Rattling, a ragged idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you your fuel is no longer acting like diesel. Stop where you are — on the verge on Chipstead Road, at the kerb, down a side road — and don't move it again. Long-term damage is very uncommon when a car is stopped early, and the fuel drain and flush that still come first take care of it.
What Short Heath motorists get told about petrol in a diesel — and the stories in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed by topping up — you're left with a fuller tank, still the same mix. A diesel fuel system does not accept petrol by percentage in the way that advice assumes.
Myth: a newer diesel copes with a bit of petrol. Rather, the opposite. Protection matters more on modern diesels, not less, since their fuel passes through finer parts at higher pressure.
Myth: "If it starts and drives, there's no damage done." This is the one that fools people. Diesel in a petrol motor usually leaves a motor that won't run: the driver stops, and so does the damage. While your pump wears, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different fault. It does not put back what petrol has diluted, and that petrol is still inside your tank later.
Myth: "Drain your tank yourself and you're sorted." Once the engine has run, some of the petrol is no longer in your tank: it's in the filter and your lines, and it goes straight back through the pump on your next start. Draining petrol into a can by the roadside is also truly dangerous.
Why petrol in a diesel happens so easily
Carelessness is seldom the cause, and nobody means to do it. A diesel nozzle generally will not fit a petrol motor, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and only in one direction.
When routine and the car stop matching, it occurs. A vehicle that is new to you — a hire car, on loan as a courtesy car, or brand new. One petrol and one diesel on the drive of the same household. Your normal forecourt, its pumps now in a different order. Racing for a train outside Erdington and fuelling up en route. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver accustomed to petrol: precisely when it happens. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of children.
Preventing petrol in a diesel next time you fill up in Short Heath
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most generally do. Read the petrol pump's label; the colour is only a hint.
- Many cars state the fuel inside your filler flap or on the cap, so check there on your first fill in a car you do not know.
- One of each in the house? Mark the key to the diesel — a coloured fob, a sticker — because intending to remember isn't enough.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It seems silly and it does the trick.
- Mistakes like this are easy to make whilst your mind is on something else, so your phone goes away.
- Add-on devices are available for vehicles without one, and some diesels are built with a filler that won't take a petrol nozzle. Useful — but a safety net at best, never a reason to stop checking the label.
- Less petrol makes a thinner blend, and so stop as soon as you notice — though remembering that the next step is unchanged. It's still not to fire it up.
Already put petrol in a diesel around Short Heath?
The order of things is short, then. Leave it unstarted, with your ignition off as well. Ask the attendants to help you push it away from the pump if you are still at the forecourt, whether that's BP or somewhere else. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
Say so if it was AdBlue instead of petrol: it's a different issue, with its own page for Short Heath, because AdBlue brings corrosion and deposits rather than lost protection.
One petrol in a diesel task in Short Heath costs more than another. Why?
There is no fair single price for this, since the four situations above are four different jobs. Which of them you are in is chiefly what moves your cost. Two things come after that: the petrol that got in as a proportion of what your tank takes, then the spot your car is in and whether our van can get to it safely.
What went in, how much, and if it's run — three queries our engineers ask before quoting, not after, for precisely that reason. With those replies, there is a straight figure instead of a range.
About Short Heath itself
Short Heath is a suburban area in the West Midlands, situated approximately 4.4 miles north of Birmingham city centre. Short Heath sits at an elevation of around 118 metres, with its semi-detached housing stock characteristic of the local residential landscape. Short Heath is bordered by nearby places such as Perry Common, Oscott, and Stockland Green, and is home to a population of around 9143 people.
Fuel drain cover in Short Heath and across West Midlands
Short Heath rests in the B postcode area, and our teams that answer petrol in diesel calls there work the places around it as well — Perry Common, Oscott and Stockland Green among them. The car doesn't need to come to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Still at the pump in Short Heath?
In that case, you couldn't be in a better spot. Leave the vehicle switched off, then ring.